Modular screen panels for use on the screen decks of vibratory screens which are used for de-watering, size classification and generally washing, drain and rinse applications of particulate material are conventionally made from a wear resistant plastics material such as polyurethane with each panel on a screen deck including formations by means of which it is releasibly engageable with the frame of the screen deck. The formations on the panels are in the form of downwardly directed headed pegs which are either moulded to be integral with the panels or are loose components which are passed through holes in the panels or between adjacent panels on the deck to be press located in holes in the screen deck frame. One of the principle disadvantages to screen panels of the above type is that the screen deck which supports them needs to be accurately holed for precise location of the panels thus making the decks of machines of this type unnecessarily expensive.